have a 1999 cherokee w/ a np231 j t case ans is leaking fluid form the rear drive shaft seal .... the questions is sould i replace the seal or rebuild the whole thing???? cost on parts is about $40 to replace seal and around $120 to rebuild btw has about 275k ( i think bought used
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If it was me, i would just replace the rear seal unless the T case is giving you issues shifting into 4WD or popping out of 4WD.

 

did my 231 with 300k about a week ago cause it wouldn't stay in 4H turns out the plastic keepers on the shift forks were completely gone not to mention the pump filter was completely clogged so in my opinion it wouldn't be a waste of time or money i mean u can split the case while still on the tranny and check it out even if it doesnt need a rebuild a little goop and its back together but more than likely u'll find something thats worn out with that many miles on it thats my 2 cents sorry for the long response lol

 

Damn where you buying parts at? Shouldn't be that high for a rear output seal. If you ever plan to do a sye i would just do the seal now and rebuild it then.